Google is rethinking some of its advertising policies after coming under fire in the UK.

Some advertising customers in the UK have pulled ads from Google-owned YouTube after some of them reportedly appeared alongside inappropriate and extremist content. The list of clients includes the British government and big brands in the UK, such as the Guardian newspaper.

For example, one British government ad was reportedly used with videos of former Ku Klux Klan leader David Duke.

Google said Friday it's begun a "thorough review" of its advertising policies. The company also said it will be giving brands more control over where their ads appear on YouTube, as well as throughout the rest of Google's ad network in the coming weeks.

"With millions of sites in our network and 400 hours of video uploaded to YouTube every minute, we recognize that we don't always get it right," Ronan Harris, managing director of Google UK, wrote in a blog post. "In a very small percentage of cases, ads appear against content that violates our monetization policies. We promptly remove the ads in those instances, but we know we can and must do more."

A representative for the UK Cabinet Office didn't immediately respond to a request for comment.

The Guardian said the ad placements by Google and YouTube are "unacceptable."

"We have stopped all advertising through Google with immediate effect until we receive guarantees that this won't happen in the future," a Guardian News and Media spokesperson said in a statement. "There is an urgent need for the industry to come together to develop a meaningful system of self-regulation."

The spokesperson declined to further comment on Google's announcement that it will revamp its ad policies.

The move comes as tech companies like Google and Facebook try to grapple with their outsize influence in media and politics. Both have been criticized for their handling of fake news, and both have amended their advertising policies to try to curb its distribution.

"We take it seriously, in terms of understanding how our product is used, the implications," she said.

"Obviously one of the challenges is you can't always understand what the downstream effects are going to be of that technology -- what that use is going to be," she continued. "Part of it is making sure that you're willing to be changed and you're willing to be flexible. You're willing to understand and you're willing to keep investing and be sure the platforms are doing the right things."

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